FRANÇAIS
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A partner speaks out
Supplement to the interview with Dominique Vernay [Thales]
Turbulence Detecting Lidars
Atmospheric turbulence is an issue for air transport comfort and safety. This phenomenon may have several causes: the closeness of clouds, variations in local temperatures, orographic waves… pilots know these areas well and avoid them for the well-being of their passengers. But, can turbulence be detected when it occurs in front of the aircraft in flight and in clear air?
Yes, using a lidar.
The principle
A lidar is a laser coupled with a sensor. It analyses the laser light reflected by the molecules encountered. It measures either the variation in the density of the air or the speed of the molecules by the Doppler effect. In this way, sudden variations in the wind field in front of the aircraft are detected.
The advantages
- Direct detection of turbulence in clear air, i.e. without the presence of drops or aerosols (traditional meteorological radar has a long range but only sees clouds).
- The setting up of a surveillance network on a planetary scale using airborne lidars and communications between users. In the long term, the generalized use of atmospheric lidar will improve knowledge of the environment, as was the case with the TAWS surveillance system (Collision with the ground, traffic and meteorological surveillance).
The difficulties
Airborne lidar must have a long enough detection range to enable the aircraft to avoid the areas of turbulence. But the current weight and size of such long range devices are still totally impractical.
Onera research bench (Theoretical and Applied Optics Department)
with a Rayleigh lidar for measuring air parameters
The research efforts
They are part and parcel of our response to the needs of airlines.
- In the long term, aircraft should be able to detect turbulences up to 50 Km in front of the aircraft and therefore be able to avoid it.
- In the medium term, a range of 10 to 20 Km in front of the aircraft should be achievable. This is the equivalent of two to three minutes flight and leaves enough time to prepare the cabin in order to minimize discomfort and the risk of injury to passengers.
- In the short term, it will be possible to detect turbulence just in front of the aircraft and manage the flight controls as a consequence: the aircraft will be able to "make the best of it" automatically.
Industrial development
A European consortium has associated a number of partners (Thales, Onera, DLR, CNRS, etc.) for developing this lidar. The preliminary work started four years ago. Onera is a partner of Thales for the system modeling aspects and a partner of CNRS for atmospheric turbulence data acquisition and modeling. Onera's expertise in lidar design and end-to-end modelling are key factors for industrial success.
The next steps
The principle of detection must be validated in different configurations and an airborne demonstrator built.
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Contact
Links
Interview with Dominique Vernay
Passive Radars
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The Thales Group website
ONERA's
Electromagnetism and Radar Departement
ONERA'sTheoretical and Applied Optics Departement
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